Brachyscelus Bate, 1861

Zeidler, Wolfgang, 2016, A review of the families and genera of the superfamily PLATYSCELOIDEA Bowman & Gruner, 1973 (Crustacea: Amphipoda: Hyperiidea), together with keys to the families, genera and species, Zootaxa 4192 (1), pp. 1-136 : 47

Key to the species of the genus Brachyscelus Bate, 1861

1. Head round in males (like female). Gnathopod 1; carpus with antero-distal corner developed into feeble lobe. Telson as long as wide................................................................................................ 2

- Head pointed in males. Gnathopod 1; carpus with antero-distal corner developed into distinct lobe, partly overlapping propodus (especially in mature specimens). Telson longer than wide.................................................. 3

2. Head as long as first five pereonites or less. Pereopod 6; basis with rounded antero-distal lobe. Telson about as long as double urosomite........................................................................ B. globiceps ( Claus 1879)

- Head as long as pereon. Pereopod 6; basis with pointed antero-distal lobe. Telson length about two-thirds double urosomite......................................................................... B. macrocephalus Stephensen, 1925

3. Pereopod 6; basis with antero-distal lobe reaching well beyond ischium, with straight distal margin. Double urosomite about as broad as long. Uropod 3 with broad exopoda and endopoda, particularly the endopoda............ B. crusculum Bate, 1861

- Pereopod 6; basis with antero-distal lobe only reaching middle, or limit, of ischium, with round distal margin. Double urosomite distinctly broader than long. Uropod 3; exopoda and endopoda not especially broad........................... 4

4. Gnathopoda with carpal process with single row of large teeth. Pereopod 7; basis as long as following articles combined. Uropod 3; endopod slightly excised distally (as in B. crusculum ). Male A2; terminal article very short, much less than half-length of preceding article.................................................................. B. rapax ( Claus, 1871)

- Gnathopoda with carpal process with large teeth interspersed with smaller ones. Pereopod 7; basis slightly longer than following articles combined. Uropod 3; endopod tapers gradually. Male A2; terminal article about half-length of preceding article............................................................................. B. rapacoides Stephensen, 1925